stack/packages/mosaic/framework/tools/wake/preimage.sh

#!/usr/bin/env bash
# preimage.sh — A11 of the wake canon (#958): durable PROVENANCE for the
# OPERATOR-SIDE preimage definition.
#
# THE GAP THIS CLOSES (#958): every observed_hash in the lane store is
# sha256(adapter stdout) — the operator's source adapter (plus the watch-list
# and any operator-declared preimage files) IS the preimage definition for
# every hash the pipeline ever records. Those files live OUTSIDE the versioned
# wake component, so a byte change to them was attributable only through agent
# transcripts: provenance thinner than any hash it feeds. A changed preimage
# also re-baselines EVERY source at once, which previously surfaced only as N
# per-source deltas / UNACCOUNTED lines with no first-class cause.
#
# WHAT THIS TOOL DOES:
#   - Derives the PREIMAGE SET generically (no operator paths baked in):
#       * the resolved file behind WAKE_DETECTOR_SOURCE_CMD (first word),
#       * the WAKE_WATCH_LIST file,
#       * operator-declared extras via WAKE_PREIMAGE_EXTRA (colon-separated —
#         e.g. sink/feed scripts). Extras are RECORD-ONLY by default (see the
#         credential hard gate below); never list key-material files.
#   - Records each file's (sha256, size, mtime, ts) as an APPEND-ONLY ledger
#     row in <state>/preimage/preimage-ledger.jsonl and stores the full bytes
#     CONTENT-ADDRESSED at <state>/preimage/objects/<sha256> — so a change is
#     attributable (prior bytes + change time) from durable state alone, with
#     no transcript required. Acceptance (a) of #958.
#   - On a CHANGE (not first-seen), `check --enqueue` enqueues ONE first-class
#     class=actionable entry per changed file via the store's single allocator
#     (#908), carrying a §2.1 hard locator (`path`), BEFORE the per-source
#     deltas it explains are observed — so the digest shows the cause line,
#     not just N re-baselined sources. Acceptance (c).
#
# CREDENTIAL HARD GATE — acceptance (b): the mechanism must be UNABLE to
# capture credential material even by operator error. Layered, every layer
# fail-closed toward NOT capturing bytes (the hash/size/mtime row is still
# written — change-time attribution survives, content capture does not;
# a sha256 discloses nothing about the bytes):
#   1. POLARITY (#964 review, case D): byte capture is DENY-BY-DEFAULT for
#      operator extras. WAKE_PREIMAGE_EXTRA paths are RECORD-ONLY (rows +
#      first-class change entries, no bytes) unless explicitly listed in
#      WAKE_PREIMAGE_CAPTURE — a shape list can only refuse the secrets
#      someone already enumerated, so arbitrary operator-pointed files must
#      not default to capture. The CORE set (the resolved adapter file, the
#      watch-list) is capture-eligible: it IS the preimage definition this
#      tool exists to snapshot, and the deny layers below still apply to it.
#   2. PATH deny: the mosaic credential store locations
#      (<mosaic-home>/credentials.json, <mosaic-home>/tools/_lib/
#      credentials.json, anything under <mosaic-home>/credentials/, and any
#      file literally named credentials.json) are refused. Evaluated on BOTH
#      the operator-supplied form AND the symlink-resolved form, against BOTH
#      the unresolved and resolved forms of the mosaic-home anchor — a deny
#      list written only in unresolved paths cannot match a path that was
#      resolved before it arrived (#964 review, case C).
#   3. CONTENT deny: a candidate whose bytes match the well-known secret-token
#      shapes (same conservative set digest.sh redacts: PAT/Slack/AKIA/JWT/PEM)
#      OR a named-assignment secret shape (key/token/secret/passw/hmac/
#      credential/bearer = long unbroken value — catches prefix-less
#      high-entropy keys, e.g. an HMAC key in an env file) is refused —
#      refusal, not redaction: a redacted preimage would be a false witness,
#      and secret bytes must never land in the object store. Deliberately
#      conservative toward REFUSAL: a false match only withholds byte capture,
#      never tracking.
#   Plus a size cap (WAKE_PREIMAGE_MAX_BYTES, default 1 MiB) so a stray extra
#   pointing at a large binary cannot turn provenance into data hoovering.
#   Deny ALWAYS wins over the WAKE_PREIMAGE_CAPTURE opt-in.
#
# FAIL-LOUD DISCIPLINE (the D2/#955 class, both layers): an infrastructure
# failure of THIS tool (unresolvable adapter, unreadable/corrupt ledger,
# failed durable write, failed enqueue) exits NON-ZERO and is never read as
# "no change". A corrupt ledger REFUSES to compare (and to re-baseline):
# silently restarting history would erase the very attribution this exists
# to provide. Likewise (#964 review, B11) an ABSENT/EMPTY ledger while
# objects/ still holds prior captures is DELETED HISTORY, not a first
# install — it refuses loudly instead of re-baselining, because a silent
# restart would absorb the next real change as first-seen.
#
# Operator-agnostic (framework firewall): all state via XDG/env; the deny
# list names only framework-defined credential locations, no operator hosts/
# names/secrets. This tool never prints file CONTENT to any stream.
set -uo pipefail

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
# shellcheck source=./_wake-common.sh disable=SC1091
. "$SCRIPT_DIR/_wake-common.sh"

STATE_DIR="$(wake_state_dir)"
STORE_SH="$SCRIPT_DIR/store.sh"
PRE_DIR="$STATE_DIR/preimage"
LEDGER="$PRE_DIR/preimage-ledger.jsonl"
OBJECTS="$PRE_DIR/objects"

_need_jq() {
  command -v jq >/dev/null 2>&1 || {
    echo "preimage.sh: jq is required" >&2
    exit 3
  }
}

# _hash_stdin — sha256 of stdin, first field only (portable, same fallback
# chain as detector.sh).
_hash_stdin() {
  if command -v sha256sum >/dev/null 2>&1; then
    sha256sum | awk '{print $1}'
  elif command -v shasum >/dev/null 2>&1; then
    shasum -a 256 | awk '{print $1}'
  elif command -v openssl >/dev/null 2>&1; then
    openssl dgst -sha256 | awk '{print $NF}'
  else
    echo "preimage.sh: no sha256 tool (sha256sum/shasum/openssl) available" >&2
    exit 3
  fi
}

usage() {
  cat >&2 <<'EOF'
Usage: preimage.sh <command>

Commands:
  check [--enqueue]   Compare every preimage-set file against the ledger head.
                      A changed file gets a new ledger row (+ captured bytes
                      when capture-eligible and not denied — see Environment);
                      with --enqueue each change (not first-seen) also enqueues
                      ONE first-class class=actionable store entry (hard
                      locator: path). First-seen files baseline SILENTLY (row,
                      no enqueue — same idiom as the detector's first-seen).
                      Exit 0 whether or not changes were found; non-zero ONLY
                      on infrastructure failure (never read as "no change").
  record              Alias of `check` without enqueue (baseline/refresh).
  set                 Print the derived preimage set, one resolved path per
                      line (diagnostic).
  status              Print the ledger head row for every tracked path.

Environment:
  WAKE_DETECTOR_SOURCE_CMD  Adapter command; its resolved file joins the set.
  WAKE_WATCH_LIST           Watch-list path; joins the set when set.
  WAKE_PREIMAGE_EXTRA       Colon-separated additional operator preimage files
                            (e.g. sink/feed scripts). Extras are RECORD-ONLY
                            by default: changes get a hash/size/mtime row and
                            a first-class change entry, but their BYTES are
                            never captured unless the path is also listed in
                            WAKE_PREIMAGE_CAPTURE. A listed path that does not
                            exist is tracked as ABSENT (deletion of a preimage
                            file is a change, not an error).
  WAKE_PREIMAGE_CAPTURE     Colon-separated allowlist of extras whose bytes
                            MAY be captured. The credential deny rules ALWAYS
                            win over this list. NEVER list files that can hold
                            key material (env files with keys/HMACs, credential
                            stores): the deny gate is a backstop, not a
                            license.
  WAKE_PREIMAGE_MAX_BYTES   Byte-capture cap (default 1048576). Larger files:
                            hash/size/mtime recorded, bytes refused.
  WAKE_STATE_HOME/WAKE_AGENT  store namespace (see store.sh).
EOF
}

# --- preimage-set derivation (generic; no operator paths baked in) ----------

# _realpath_or_self PATH — resolved form when resolvable, the input otherwise.
_realpath_or_self() {
  local p="$1"
  if command -v realpath >/dev/null 2>&1; then
    realpath -- "$p" 2>/dev/null || printf '%s' "$p"
  else
    printf '%s' "$p"
  fi
}

# _resolve_cmd_file CMD — resolve the FIRST WORD of an adapter command string
# to a real file; prints `raw<TAB>resolved`. Non-zero (loud) if it cannot be
# resolved: an adapter the detector will invoke but provenance cannot see is
# an infrastructure failure, not a smaller set. BOTH forms are kept: the deny
# gate must see the pre-resolution form too (#964 review, case C).
_resolve_cmd_file() {
  local cmd="$1" word path
  # shellcheck disable=SC2086
  set -- $cmd
  word="${1:-}"
  [ -n "$word" ] || return 1
  if [ -f "$word" ]; then
    path="$word"
  else
    path="$(command -v -- "$word" 2>/dev/null)" || return 1
    [ -f "$path" ] || return 1
  fi
  # realpath so the ledger keys on the actual file, not a symlink alias.
  printf '%s\t%s' "$path" "$(_realpath_or_self "$path")"
}

# _preimage_set — print the derived set, one member per line as
# `origin<TAB>raw<TAB>resolved` (origin: core|extra). BOTH path forms travel
# with every member so the deny gate and the capture allowlist are evaluated
# on the SAME candidate in BOTH its forms — resolving before denying is the
# #964 case-C ordering defect. Paths from WAKE_PREIMAGE_EXTRA are printed
# EVEN IF ABSENT (deletion is a tracked state); the adapter and watch-list
# must resolve (loud failure otherwise — see _resolve_cmd_file rationale).
_preimage_set() {
  local failed=0
  if [ -n "${WAKE_DETECTOR_SOURCE_CMD:-}" ]; then
    local af
    if af="$(_resolve_cmd_file "$WAKE_DETECTOR_SOURCE_CMD")"; then
      printf 'core\t%s\n' "$af"
    else
      echo "preimage.sh: FAIL LOUD — WAKE_DETECTOR_SOURCE_CMD ('$WAKE_DETECTOR_SOURCE_CMD') does not resolve to a file; the preimage definition cannot be observed (NOT treated as 'no change')." >&2
      failed=1
    fi
  fi
  if [ -n "${WAKE_WATCH_LIST:-}" ]; then
    if [ -f "$WAKE_WATCH_LIST" ]; then
      printf 'core\t%s\t%s\n' "$WAKE_WATCH_LIST" "$(_realpath_or_self "$WAKE_WATCH_LIST")"
    else
      echo "preimage.sh: FAIL LOUD — WAKE_WATCH_LIST ('$WAKE_WATCH_LIST') is not a file; the preimage definition cannot be observed." >&2
      failed=1
    fi
  fi
  if [ -n "${WAKE_PREIMAGE_EXTRA:-}" ]; then
    local IFS=':' p
    for p in $WAKE_PREIMAGE_EXTRA; do
      [ -n "$p" ] || continue
      # Extras are tracked even when absent (ABSENT is a state). Resolve the
      # realpath only when the file exists; otherwise track the literal path.
      if [ -e "$p" ]; then
        printf 'extra\t%s\t%s\n' "$p" "$(_realpath_or_self "$p")"
      else
        printf 'extra\t%s\t%s\n' "$p" "$p"
      fi
    done
  fi
  return "$failed"
}

# --- credential hard gate (acceptance (b)) ----------------------------------

# _deny_path RAW RESOLVED — 0 (deny) iff EITHER form of the candidate names a
# known credential-store location. Framework-defined locations only
# (firewall): the mosaic credential store, the tools/_lib credential file the
# framework-manifest itself carves out of tools/**, the credentials/ operator
# subtree, and any file literally named credentials.json.
#
# Evaluated on BOTH the operator-supplied (raw) form and the symlink-resolved
# form, against BOTH the unresolved and resolved forms of the mosaic-home
# anchor: a deny list written only in unresolved paths cannot match a path
# that was resolved before it arrived (#964 review, case C — a symlink whose
# target was renamed slipped every path rule because the candidate had
# already been realpath'd but the anchors never were).
_deny_path() {
  local raw="$1" resolved="$2"
  local home="${MOSAIC_HOME:-$HOME/.config/mosaic}" rhome p a
  rhome="$(_realpath_or_self "$home")"
  for p in "$raw" "$resolved"; do
    [ -n "$p" ] || continue
    for a in "$home" "$rhome"; do
      case "$p" in
      "$a/credentials.json") return 0 ;;
      "$a/tools/_lib/credentials.json") return 0 ;;
      "$a/credentials/"*) return 0 ;;
      esac
    done
    case "$(basename -- "$p")" in
    credentials.json) return 0 ;;
    esac
  done
  return 1
}

# _deny_content FILE — 0 (deny) iff FILE's bytes look secret-shaped.
# Two probes: (a) the well-known vendor-token shapes digest.sh redacts
# (PAT / Slack / AKIA / JWT / PEM — conservative: a 40-hex git sha never
# matches); (b) a named-assignment shape (key/token/secret/passw/hmac/
# credential/bearer = long unbroken value) that catches prefix-less
# high-entropy keys, e.g. an HMAC key in an env file (#964 review, case D).
#
# (b) is defense-in-depth for the OPT-IN path only, NOT the thing that keeps
# case D safe — polarity does that (extras are record-only unless allowlisted;
# a shape list can only refuse the secrets someone already enumerated). It is
# deliberately conservative toward REFUSAL: a false match (a checksum in a
# config, a path that happens to be long and unbroken) only withholds byte
# capture — the hash/size/mtime row and change entry still land. A variable
# REFERENCE (token="$GITEA_TOKEN") never matches: `$` is not in the value
# class — only literal secret values do.
#
# FAILS TOWARD REFUSAL: if a probe itself errors (unreadable file, grep
# failure — rc >= 2), the answer is DENY, not capture. An error exit is not a
# negative result.
_deny_content() {
  local rc
  LC_ALL=C grep -Eq \
    -e 'gh[pousr]_[A-Za-z0-9]{16,}' \
    -e 'github_pat_[A-Za-z0-9_]{16,}' \
    -e 'xox[baprs]-[A-Za-z0-9-]{10,}' \
    -e 'AKIA[0-9A-Z]{16}' \
    -e 'eyJ[A-Za-z0-9_-]{8,}\.[A-Za-z0-9_-]{8,}\.[A-Za-z0-9_-]{8,}' \
    -e '-----BEGIN[A-Z ]*PRIVATE KEY-----' \
    -- "$1" 2>/dev/null
  rc=$?
  [ "$rc" -eq 1 ] || return 0
  LC_ALL=C grep -Eiq \
    -e "[A-Za-z0-9_]*(key|token|secret|passw|hmac|credential|bearer)[A-Za-z0-9_]*[[:space:]]*[=:][[:space:]]*[\"']?[A-Za-z0-9+/=_-]{16,}" \
    -- "$1" 2>/dev/null
  rc=$?
  [ "$rc" -eq 1 ] || return 0
  return 1
}

# _capture_allowed ORIGIN RAW RESOLVED — 0 iff byte capture may even be
# ATTEMPTED for this member (the deny gate still runs after, and wins).
# POLARITY (#964 review, case D): core members (the adapter file, the
# watch-list) are capture-eligible — they ARE the preimage definition this
# tool exists to snapshot (acceptance (a)). Extras are RECORD-ONLY unless
# listed in WAKE_PREIMAGE_CAPTURE.
#
# The allowlist is matched with the SAME both-forms discipline as the deny
# list (entry raw/resolved vs candidate raw/resolved): two lists keyed on
# different strings would let a symlink alias slip between them. "Deny wins
# over opt-in" is a precedence rule, not a guarantee both lists see the same
# path — the guarantee comes from _check_one running _deny_path on both forms
# FIRST, independent of anything matched here.
_capture_allowed() {
  local origin="$1" raw="$2" resolved="$3"
  [ "$origin" = "core" ] && return 0
  [ -n "${WAKE_PREIMAGE_CAPTURE:-}" ] || return 1
  local IFS=':' e er
  for e in $WAKE_PREIMAGE_CAPTURE; do
    [ -n "$e" ] || continue
    er="$e"
    [ -e "$e" ] && er="$(_realpath_or_self "$e")"
    if [ "$e" = "$raw" ] || [ "$e" = "$resolved" ] ||
      [ "$er" = "$raw" ] || [ "$er" = "$resolved" ]; then
      return 0
    fi
  done
  return 1
}

# --- ledger primitives ------------------------------------------------------

# _ledger_head PATH — print the LAST ledger row for PATH (empty if none).
# Non-zero (loud) if the ledger exists but is unparseable: a corrupt ledger
# must REFUSE to compare, never silently re-baseline (that would erase the
# attribution history this tool exists to keep).
_ledger_head() {
  local path="$1"
  [ -f "$LEDGER" ] || return 0
  if [ -s "$LEDGER" ] && ! jq -cn 'inputs' <"$LEDGER" >/dev/null 2>&1; then
    echo "preimage.sh: FAIL LOUD — preimage ledger $LEDGER is unparseable; REFUSING to compare or re-baseline over corrupt history. Investigate/restore the ledger." >&2
    return 1
  fi
  jq -c --arg p "$path" 'select(.path == $p)' "$LEDGER" 2>/dev/null | tail -n 1
}

# _ledger_append ROW_JSON — append one row atomically (read + append + rename;
# rows are small and the writer is serialized by the preimage lock).
_ledger_append() {
  local row="$1"
  {
    [ -f "$LEDGER" ] && cat "$LEDGER"
    printf '%s\n' "$row"
  } | _atomic_write "$LEDGER"
}

# --- the check itself -------------------------------------------------------

# _check_one ORIGIN RAW PATH ENQUEUE — compare PATH (the resolved form; the
# ledger keys on it) to its ledger head; on change record (+bytes only if
# capture-eligible and not denied) and optionally enqueue. Prints nothing on
# no-change. Returns: 0 ok (changed or not), 1 infrastructure failure.
_check_one() {
  local origin="$1" raw="$2" path="$3" enqueue="$4"
  local cur_sha size mtime denied="" refused=""

  if [ -f "$path" ]; then
    cur_sha="$(_hash_stdin <"$path")" || return 1
    [ -n "$cur_sha" ] || {
      echo "preimage.sh: FAIL LOUD — could not hash $path" >&2
      return 1
    }
    size="$(wc -c <"$path" | tr -d '[:space:]')"
    # Portable mtime (GNU stat -c / BSD stat -f).
    mtime="$(stat -c %Y -- "$path" 2>/dev/null || stat -f %m -- "$path" 2>/dev/null || echo 0)"
    local cap="${WAKE_PREIMAGE_MAX_BYTES:-1048576}"
    case "$cap" in '' | *[!0-9]*) cap=1048576 ;; esac
    # Gate order matters: path deny FIRST, on BOTH forms, INDEPENDENT of the
    # capture allowlist — so an allowlisted symlink whose target is denied
    # refuses no matter what string the allowlist matched (a known credential
    # store is refused without a content probe; the hash read above is
    # deliberate: a sha256 discloses nothing about the bytes). Then polarity
    # (record-only extras never reach the content probe — case D must be safe
    # WITHOUT the shape list), then size cap (never content-grep an oversized
    # file), content shape last.
    if _deny_path "$raw" "$path"; then
      denied="credential-store path (deny list)"
    elif ! _capture_allowed "$origin" "$raw" "$path"; then
      denied="extra is record-only by default (byte capture requires WAKE_PREIMAGE_CAPTURE; deny rules still win)"
    elif [ "$size" -gt "$cap" ]; then
      denied="exceeds WAKE_PREIMAGE_MAX_BYTES ($size > $cap)"
    elif _deny_content "$path"; then
      denied="secret-shaped content"
    fi
  else
    # ABSENT is a state (deletion of a preimage file is a change to record).
    cur_sha="ABSENT"
    size=0
    mtime=0
  fi

  local head prev_sha=""
  head="$(_ledger_head "$path")" || return 1
  [ -n "$head" ] && prev_sha="$(jq -r '.sha256 // ""' <<<"$head")"

  if [ "$cur_sha" = "$prev_sha" ]; then
    return 0 # unchanged — no row, no enqueue (idempotent)
  fi

  # --- capture bytes (content-addressed) unless the hard gate refuses -------
  local captured=true
  if [ "$cur_sha" != "ABSENT" ]; then
    if [ -n "$denied" ]; then
      captured=false
      refused="$denied"
      echo "preimage.sh: byte capture WITHHELD for $path ($denied) — hash/size/mtime recorded, content NOT stored (#958)." >&2
    else
      mkdir -p "$OBJECTS" || return 1
      if [ ! -f "$OBJECTS/$cur_sha" ]; then
        if ! _atomic_write "$OBJECTS/$cur_sha" <"$path"; then
          echo "preimage.sh: FAIL LOUD — durable object write failed for $path ($OBJECTS/$cur_sha); NO ledger row recorded (a row whose bytes were never durably kept would be a false witness)." >&2
          return 1
        fi
      fi
    fi
  fi

  local ts row
  ts="$(date +%s)"
  row="$(jq -cn \
    --arg path "$path" \
    --arg sha "$cur_sha" \
    --arg prev "$prev_sha" \
    --argjson size "$size" \
    --argjson mtime "$mtime" \
    --argjson ts "$ts" \
    --argjson captured "$captured" \
    --arg refused "$refused" \
    '{ts:$ts, path:$path, sha256:$sha, size:$size, mtime:$mtime, captured:$captured}
       + (if $prev != "" then {prev:$prev} else {} end)
       + (if $refused != "" then {refused:$refused} else {} end)')" || return 1
  if ! _ledger_append "$row"; then
    echo "preimage.sh: FAIL LOUD — durable ledger append failed ($LEDGER)" >&2
    return 1
  fi

  if [ -z "$head" ]; then
    # First-seen: baseline SILENTLY (row only, no enqueue) — the same idiom as
    # the detector's first-seen source baseline.
    return 0
  fi

  echo "preimage.sh: preimage definition CHANGED — $path ($prev_sha -> $cur_sha); prior bytes: $OBJECTS/$prev_sha" >&2

  if [ "$enqueue" = "1" ]; then
    # First-class cause line (acceptance (c)): ONE class=actionable entry per
    # changed preimage file, allocated by the store's single allocator (#908).
    # `path` is a §2.1 hard locator, so the digest renders it — never
    # quarantined. Callers run this BEFORE polling sources, so this seq is
    # LOWER than the per-source deltas the change explains.
    local locators
    locators="$(jq -cn \
      --arg path "$path" \
      --arg sha "$cur_sha" \
      --arg prev "$prev_sha" \
      '{kind:"preimage", id:$path, path:$path, observed_hash:$sha, prev_hash:$prev,
        preimage:true, reason:"preimage-definition-changed"}')"
    if ! "$STORE_SH" enqueue --class actionable --locators "$locators" --emit-ts "$(date +%s)" >/dev/null; then
      echo "preimage.sh: FAIL LOUD — store enqueue of the preimage-change entry FAILED for $path (the change IS recorded in the ledger; the first-class wake line is NOT — treat as infrastructure failure)." >&2
      return 1
    fi
  fi
  return 0
}

cmd_check() {
  local enqueue=0
  while [ $# -gt 0 ]; do
    case "$1" in
    --enqueue)
      enqueue=1
      shift
      ;;
    *)
      echo "preimage.sh check: unknown option '$1'" >&2
      exit 2
      ;;
    esac
  done
  _need_jq

  local set_list
  if ! set_list="$(_preimage_set)"; then
    exit 1
  fi
  if [ -z "$set_list" ]; then
    # Nothing declared (no adapter/watch-list/extras in env) — an empty set is
    # a no-op, not an error: standalone invocations outside a wake runtime
    # must not fail loud for lacking one.
    return 0
  fi

  mkdir -p "$PRE_DIR" || exit 1
  # Serialize concurrent checks (detector tick vs reconcile vs manual) — the
  # ledger append is read+rewrite, so two writers must not interleave.
  if ! _wake_lock_acquire "$PRE_DIR/preimage.lock"; then
    echo "preimage.sh: FAIL LOUD — cannot acquire preimage lock" >&2
    exit 1
  fi
  # #964 review (B11): an ABSENT/EMPTY ledger while objects/ still holds
  # prior captures is DELETED HISTORY, not a first install — the asymmetry is
  # locally detectable and is the whole detection. Re-baselining here would
  # silently absorb the next real change as first-seen (the exact erasure
  # this tool exists to prevent). ABSENT is not CORRUPT: it must not take the
  # first-install path either.
  if [ ! -s "$LEDGER" ] && [ -d "$OBJECTS" ] && [ -n "$(ls -A -- "$OBJECTS" 2>/dev/null)" ]; then
    echo "preimage.sh: FAIL LOUD — preimage ledger $LEDGER is ABSENT/EMPTY but $OBJECTS still holds prior objects: history was deleted; REFUSING to re-baseline over it (a silent restart would absorb the next real change as first-seen). Restore the ledger, or move objects/ aside explicitly after investigation." >&2
    _wake_lock_release
    exit 1
  fi
  local failed=0 origin raw resolved
  while IFS=$'\t' read -r origin raw resolved; do
    [ -n "$resolved" ] || continue
    _check_one "$origin" "$raw" "$resolved" "$enqueue" || failed=1
  done <<EOF
$set_list
EOF
  _wake_lock_release
  [ "$failed" -eq 0 ] || exit 1
}

cmd_status() {
  _need_jq
  [ -f "$LEDGER" ] || {
    echo "preimage.sh: no ledger yet ($LEDGER)" >&2
    return 0
  }
  # Head row per path (last wins).
  jq -cs 'group_by(.path) | map(last) | .[]' "$LEDGER"
}

cmd_set() {
  local s
  s="$(_preimage_set)" || exit 1
  [ -n "$s" ] && printf '%s\n' "$s" | cut -f3
}

main() {
  [ $# -ge 1 ] || {
    usage
    exit 2
  }
  local cmd="$1"
  shift
  case "$cmd" in
  check) cmd_check "$@" ;;
  record) cmd_check ;;
  set) cmd_set "$@" ;;
  status) cmd_status "$@" ;;
  -h | --help | help) usage ;;
  *)
    echo "preimage.sh: unknown command '$cmd'" >&2
    usage
    exit 2
    ;;
  esac
}

main "$@"